Antioxidants Explained: Why These Compounds Are So Important

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Found in many foods, antioxidants fight the oxidation process, a chemical reaction that can cause damage to many cells in your body

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A lot of hype surrounds a group of compounds found in food called antioxidants. They are touted as everything from disease fighters to memory protectors to the antidote to aging. What are these compounds? Why are they important? And should you take supplements to get enough (or more) in your diet?

WHAT IS AN ANTIOXIDANT?

Antioxidants help fight oxidation, a normal chemical process that takes place in the body every day. It can be accelerated by stress, cigarette smoking, and alcohol. When there are disruptions in the natural oxidation process, highly unstable and potentially damaging molecules called free radicals are created. Oxygen triggers the formation of these destructive little chemicals, and, if left uncontrolled, they can cause damage to cells in the body. It's much like the chemical reaction that creates rust on a bicycle or turns the surface of a cut apple brown.

Free Radicals

These free radicals are atoms or groups of atoms that contain an odd number of electrons. They can be formed when certain molecules interact with oxygen. Once formed, free radicals can start a chain of damaging chemical reactions. The biggest danger to the human body is their potential to react with cellular components like DNA or the cell membrane, causing cells to function poorly or die.

Free radicals are not only generated by the body, they are present in foods you eat as well as in the air you breathe. Some even come through exposure to sunlight that can harm the eyes and the skin. Free radicals can trap a low-density lipoprotein (LDL) in an artery wall and begin the formation of plaque; they can damage DNA; or they can change the course of what enters and leaves a cell. Any of these actions can be the start of a disease process.

How the Body Defends Against Oxidative Stress

Oxidative stress occurs when the production of free radicals goes beyond the protective defenses in the body. Oxidative stress and free radical damage to cells may initiate the early stages of cancer and heart disease. Free radicals are also suspect in the development of Alzheimer's disease, arthritis, cataracts, diabetes, kidney disease, and age-related blindness.

The human body is not without its own defenses against this damage. It creates many different types of molecules --  antioxidants -- to combat these free radicals and protect the cells from attack by oxygen. Antioxidants can safely interact with free radicals and stop the chain of damaging reactions before damage is done to cells. There are several enzyme systems in the body that scavenge free radicals, but we can also gain these helpful molecules from foods that we eat. Some vitamins are antioxidants, such as vitamins C and E. Some minerals are antioxidants, such as selenium and manganese, and there are plant compounds that act as antioxidants such as beta carotene and lycopene, terms you may have heard before or seen in ads for vitamin supplements.

ONLY CERTAIN FOODS ARE GOOD SOURCES OF ANTIOXIDANTS

Many foods are good sources of antioxidants. The table below shows several types of antioxidants, their possible effects, and food sources of each. The big thing to notice is that antioxidants are found primarily in plant foods. The antioxidant minerals, selenium and manganese, are found in small quantities in meats and seafood, but the primary food source of all antioxidants is plant foods.

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There is a huge range of antioxidant systems, and scientists haven't yet determined exactly how all the different systems work together in our bodies to protect us from free-radical damage. No one antioxidant can provide the protection offered by the many antioxidants working together.

The best way to get a variety of antioxidants in the diet is to eat foods that represent all the colors of the rainbow. Each color provides its own unique antioxidant effects. Bright orange, deep yellow fruits and vegetables like carrots, sweet potatoes, and apricots provide one type of antioxidant. Red foods like tomatoes, provide another. Green vegetables, such as broccoli and cabbage, and blue or purple foods, like blueberries and eggplant, each have their own antioxidant packages. Curcumin, the substance that makes turmeric yellow, is also believed to offer benefits.

WHAT ANTIOXIDANTS CAN -- AND CAN'T -- DO

Scientists began to theorize that free-radical damage was involved in the early stages of atherosclerosis and might play a role in the development of many other chronic medical conditions in the 1990s. Studies at the time suggested that people who ate few antioxidant-rich fruits and vegetables had a greater risk of developing these medical conditions. So began several clinical trials in which antioxidant supplements like beta carotene and vitamin E were tested for their protection against heart disease, cancer, and other conditions.

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Beth Fontenot is a registered dietitian and a licensed dietitian/nutritionist. She serves on the Louisiana Board of Examiners in Dietetics and Nutrition and writes for TheDoctorWillSeeYouNow.com.

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